WinINet Support for Negotiate Auth to a Proxy Server in Windows Vistahttp://blogs.msdn.com/b/wndp/archive/2006/04/07/571217.aspxBy default WinINet supports the following authentication schemes: Negotiate, NTLM, Digest and Basic. However, in previous OS releases WinINet did not support Negotiate authentication to proxys , as it would not respond to a negotiate challenge from aen-USTelligent Evolution Platform Developer Build (Build: 5.6.50428.7875)